This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-322418, filed Nov. 12, 1999; and No. 2000-003334, filed Jan. 12, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a thermosetting resin decorative board which is used as a surface material of furniture, containers and the like or as an interior/exterior decorative material of architecture, vehicles and the like, and also relates to a method of producing the same thermosetting resin decorative board.
Conventionally, thermosetting resin decorative boards such as a melamine decorative board are widely used for various applications as described above. In order to produce a thermosetting resin decorative board, in general, a desired design pattern like wood grain pattern is at first printed on the surface of base paper having excellent water-absorbing properties (such as titania-containing paper). This product is impregnated with a thermosetting resin such as melamine resin, so as to produce patterned paper impregnated with a thermosetting resin. A sheet of core paper (produced by impregnating base paper such as kraft paper with a thermosetting resin such as phenol resin) is set on a substrate like plywood, and the pattern paper is set on the core paper. An overlay paper (produced by impregnating base paper having a characteristic of becoming transparent when impregnated with a resin, with a thermosetting resin such as a melamine resin) may be set on the patterned paper, if necessary. By hot-pressing the resulting product, a thermosetting resin decorative board is obtained.
During the hot-pressing process described above, a metal plate having a mirror-like or a desired texture-like surface is generally set on the overlay paper or the patterned paper impregnated with the thermosetting resin, so that the surface of the produced decorative board eventually has a predetermined finished state such as a mirror-like or a desired texture-like state. The method of forming raised (in relief)/recessed (concave) portions on the surface of a decorative board in such a manner is called the mechanical embossing method (refer to Japanese Patent Publication (KOKAI) No. 47-14273).
However, when a thermosetting resin decorative board having a texture-like surface is produced by the mechanical embossing method, a considerable number of the metal plates have to be prepared (the number of the metal plates must correspond to the number of types of texture to be produced), thereby significantly increasing the production cost. In addition, according to the mechanical embossing method, there arises a problem that it is extremely difficult to align (or correspond) the texture of the decorative board surface with the design pattern on the surface of the base paper.
As a non-mechanical embossing method in which the texture of the decorative board surface can be easily aligned with the design pattern, a chemical embossing method has also been developed. The chemical embossing method is characterized in that a printing ink containing a chemical substance called a curing inhibitor having an effect of delaying the curing reaction of the impregnated thermosetting resin is used as at least a portion of the printing ink for forming the design pattern (the xe2x80x9cportionxe2x80x9d of the printing ink may be a part of a pattern or a part of the colors in a case of multi-color printing). By using a printing ink which contains the curing inhibitor, curing of the thermosetting resin at the portions printed by the printing ink can be delayed during the hot-pressing process. Thereafter, by removing the resin remaining uncured after the hot-pressing process, recessed portions are formed (refer to Japanese Patent Publication (KOKAI) No. 53-110677).
The chemical embossing method has advantages that the alignment of the texture with the design pattern is easy and a single mirror-surface plate allows formation of any desired texture. However, in this method, the operation of removing the resin remaining uncured and the operation of cleaning the mirror-surface plate to which the uncured resin adhere are quite complicated, thereby reducing the productivity. Further, a specific chemical substance (ink) is required. Accordingly, significant reduction of the production cost is still difficult to achieve in the chemical embossing method.
As yet another embossing method, there has been proposed a method of forming recessed portions by inserting a transfer sheet having a transfer layer of liquid repellent patterns formed by a liquid repellent ink between the mirror-surface plate and the thermosetting resin impregnated paper, during the hot-pressing process of the thermosetting resin decorative board; transferring the liquid repellent patterns onto the product surface, simultaneous with the hot-pressing process; coating the whole surface with a transparent paint; and letting the transparent paint being repelled by the liquid repellent patterns, thereby forming recessed portions (refer to Japanese Patent Publication (KOKAI) No. 2-284677).
However, the thermosetting resin used for the production of such a thermosetting resin decorative board is generally selected from hard resins having a relatively high cross-linking density, in consideration of the strict requirement of particular physical properties, and thus the surface of the resin after the hot-pressing and curing process exhibits significantly poor adherency with other resins. Therefore, there arises a problem that close and reliable adhesion of the thermosetting resin surface with the transparent paint coated after the hot-pressing process is difficult to achieve and thus a thermosetting resin decorative board having excellent surface physical properties is hardly obtained.
Further, as a method for expressing a texture without creating the raised/recessed portion such as emboss, there has been proposed a method in which mat patterns, formed by a mat ink which contains a matting agent, is provided as at least a portion of the design patterns to be print-formed on the surface of the base paper (the xe2x80x9cportionxe2x80x9d of the printing ink may be a part of a pattern or a part of the colors in a case of multi-color printing) (Japanese Patent Publication (KOKAI) No. 54-120663).
This method has advantages that a single mirror-surface plate can deal with various types of texture; and decorative boards having different texture (texture is varied by changing the pattern and/or the lusterlessness of the mat ink) can be easily and efficiently produced at a low production cost without having a problem of uncured resin or the like. When a decorative board is actually produced by this method, mat patterns having a sufficient mat effect can be formed at the time of printing to the base paper. However, the mat ink is then planished due to a high pressure during the hot-pressing process and apparent raised/recessed portions on the surface are reduced, thereby not allowing the produced decorative board to have a satisfactory (or expected) texture appearance.
Therefore, in order to suppress the deterioration of gloss-mat effect by the hot-pressing process, several measures have been taken. For example, a hard particles having a relatively large diameter (2 or 3 to 90 xcexcm or so) is used as the matting agent blended in the mat ink. Or, the hot-pressing is carried out after sufficiently curing the mat patterns by using a curable resin as the binder of the mat ink (Japanese Patent Publication (KOKAI) No. 1-135637). However, these measures have not necessarily achieved sufficiently excellent results. The inventors of the present invention have studied in detail the reason why such measures failed to achieve good results and discovered that, during the hot-pressing, the uncured thermosetting resin which melts due to the heat bleeds out of the base paper, enters between the mirror-surface plate and the mat pattern, forms a film on the mat pattern, resulting in that the film covers the mat pattern and reduces its gloss-mat effect.
Accordingly, it is an object of the present invention to provide a thermosetting resin decorative board which has recessed portions aligned with design patterns and thus is excellent in designing.
Another object of the present invention is to provide a thermosetting resin decorative board having mat patterns provided on the surface of the thermosetting resin-impregnated sheet, the mat effect of the mat pattern being not reduced by the hot-pressing process, thereby achieving an excellent texture appearance due to sufficient gloss-mat differences.
A related object of the present invention is to provide a method of producing a thermosetting resin decorative board, by which a thermosetting resin decorative board which has recessed portions aligned with a design pattern and thus is excellent in designing can be easily and efficiently produced at a low production cost.
A further object of the present invention is to provide a method of producing a thermosetting resin decorative board in which the mat effect of the mat patterns is not reduced by the hot-pressing process and thus an excellent texture appearance due to sufficient gloss-mat differences is achieved.
According to a thermosetting resin decorative board of the present invention, a liquid repellent pattern and a covering layer of the impregnated resin are provided on the surface of the thermosetting resin-impregnated sheet and the covering layer of the impregnated resin is thicker than the liquid repellent pattern.
According to another thermosetting resin decorative board of the present invention, a mat pattern having liquid repellency and a covering layer of the impregnated resin having gloss are provided on the surface of the thermosetting resin-impregnated sheet.
A method of producing a thermosetting resin decorative board according to the present invention, comprises the steps of forming a liquid repellent pattern on a surface of base paper having excellent water absorbing properties; impregnating the base paper with a thermosetting resin which is repelled by the liquid repellent pattern, thereby forming a covering layer of the impregnated resin, on the base paper, at the portions other than the portions where the liquid repellent pattern is formed, such that the covering layer of the impregnated resin is thicker than the liquid repellent pattern; obtaining resin-impregnated pattern sheet in which a recessed portion is created at the portion of the liquid repellent pattern; setting the resin-impregnated pattern sheet on a substrate; and hot-pressing the product, while maintaining configuration of the recessed portion.
Another method of producing a thermosetting resin decorative board according to the present invention, comprising the steps of providing a mat pattern having liquid repellency on a base paper having excellent water absorbing properties; impregnating the base paper with a thermosetting resin which is repelled by the liquid repellent mat pattern, thereby producing a resin-impregnated pattern sheet in which a covering layer of the impregnated resin is formed, on the base paper, at the portions other than the portions where the liquid repellent mat pattern is formed; and hot-pressing the resin-impregnated pattern sheet.
Additional objects and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention.
The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.